With Internet Explorer 9, the browser becomes a tightly integrated component of the operating system, and websites become applications that extend the desktop experience to the Web. In order to deliver adequate performance and provide the functionality Microsoft delivers with IE9, you have to have a solid operating system and hardware foundation.
Yes, Microsoft may alienate customers by not providing backwards compatibility with Windows XP. But, when those customers move to Windows 7--or eventually Windows 8--they will appreciate that Microsoft had the conviction to abandon backward compatibility in favor of a more immersive and integrated Web experience.
